1. Field of the Invention
The present invention relates to apparatus for handling heavy equipment, and more particularly, the invention relates to apparatus for supporting a length of pipe to accommodate pipe stabbing or removal operations during launching or recovery of the length of pipe through an opening in a support platform on a deep ocean mining vessel.
2. Description of the Prior Art
The potential of the ocean for supplying important and basic raw materials is generally recognized. Mining operations for sand, gravel, shell and other materials from continental shelf deposits are presently being performed by dredging techniques. On the ocean floor in deeper waters are vast quantities of mineral deposits. Among these deposits are mineral concentrations spread over large areas of the ocean floor in the form of nodules. Existence of nodules on the ocean bottom has been known for many years and are believed to be formed over aeons of time due to the precipitation of the mineral substances out of the seawater. These nodules are known to consist essentially of iron oxide, manganese oxide, copper, cobalt and nickel, and are generally found in the deep areas of the sea where the floor is relatively hard and flat. The areas in which the nodules are presently known to exist in sufficient quantities to sustain a profitable mining operation are found generally more than 200 miles offshore and at depths of up to 18,000 feet and more.
Among the numerous systems which have been conceived for the recovery of nodules from the ocean floor is the hydraulic system which generally consists of a pipestring which is suspended from a floating platform or vessel. The system includes a gathering head which is designed to collect and winnow the nodules from the ocean floor sediments and transport them through the pipestring. Means are provided for causing the water inside the pipestring to flow upward with sufficient velocity to draw the nodules into the system and transport them to the surface.
One of the major problems associated with this mining method is the provision of apparatus for handling lengths of pipe during launching and recovering the pipestring which permits efficient execution of the launching and recovery operations. Since the load of a pipestring for working in depths up to 18,000 feet may exceed 5,000 kips, it will be appreciated that apparatus for handling the pipestring in such deep ocean mining operations must be capable of handling unusually large loads. Such large loads exceed the radial collapse strength of pipes typically used to make up the pipestring. Therefore conventional support apparatus of the type which engages the tubular body portion of the pipe and imposes a radial load on the wall of the pipe to prevent slipping is unsatisfactory because of the risk of collapsing or weakening the wall of the pipe.
A factor which must be considered in addition to the preservation of the structural integrity of the pipe sections is the efficient execution of the launching and recovery operations. The efficiency of the pipe handling operations depends upon such factors as the running speed of the hoist rig, the time required to make up or break a tool joint during stabbing operations, the time required to mechanically couple and decouple the hoist rig and the pipestring, and the time required to transport a length of pipe from the pipestring to a storage station during recovery operations or to transport a length of pipe from the storage station to the pipestring during launching operations. Because of the requirement that the pipestring be supported without imposing compressive loads upon the tubular body portion of the pipestring, conventional coupling devices, for example those with gripping jaws, cannot be used to perform the handling operations. As the search for ocean mineral deposits advances into deeper waters and the length of the pipestring increases to reach abyssal depths, it is essential that pipe handling equipment be provided which can safely support the unusually large load of the pipestring and which permits the efficient execution of launching and recovery operations while preserving the structural integrity of the pipestring during the handling operations.